With the conventional melt-spinning of thermoplastic multifile filaments, the freshly extruded, separate filaments or capillaries have a tendency to stick together or at least partially to fuse with one another on or immediately after the melt has issued from the extrusion nozzle. There is also a tendency for the filaments to break during the subsequent drawing out and stretching. Consequently, many different proposals have already been made for substantially preventing the sticking together and for reducing the number of filament breakages, by providing in some way or another for a rapid cooling and gentle further treatment of the separate filaments or capillaries. See, for example, German Patent No. 807,248.
The present invention follows an entirely different approach. It is based on the knowledge that the defects which formerly arose with the melt-spinning of thermoplastic multifile filaments cannot occur if the multifile filaments or capillaries are intentionally formed as part of a foil, and these are therefore initially extruded as a part of the foil which corresponds to a ribbon of several or a large number of closely juxtaposed strands. This foil is then split up into continuous uniform separate strands and/or filaments.
It has of course already previously been proposed, for textile purposes, to cut a thin web of paper, cellulose or other materials into narrow strips, (e.g., U.S. Pat. No. 2,106,896) or to orient thin foils or foil strips of thermoplastic high polymer masses by stretching and to divide them by subsequent mechanical action of various types, for example, by brushing, twisting and the like into elements of fiber form and similar to natural fiber. Such fiber formations are no longer able to satisfy the relatively high standards for further processing, on account of the irregular dimensions of the separate fibers. Various other processes are also known in which flat or longitudinally ribbed strips of foil are oriented by stretching and are split up into an irregular network of fibrillae by blowing or twisting or by the foil skin connecting the ribs being slit at various places. The fibrillae, however, remain connected to one another at more or less small intervals. See, for example German patent specifications Nos. 1,040,663 and 1,035,657.